The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating, disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information processing in the information age is increasing, rapidly. In particular, it is desired that HDDs be able to store more information in their limited area and volume. A technical approach to this desire is to increase the capacity by increasing the recording density of the HDD. To achieve higher recording density, further miniaturization of recording hits is effective, which in turn typically requires the design of smaller and smaller components.
Recently, Shingled Magnetic Recording (SMR) has been designed to be used as a recording method for improving areal density. An example of SMR is shown in FIG. 5. In this method, tracks are recorded overlapping, in as tile-like manner. As a result, tracks which are actually read out are recorded using an edge of a main pole, and the recording characteristics at the edge of the main pole are therefore more important than in other areas of the main pole. In other words, it is useful to improve the field gradient in the cross-track direction and the field gradient in the down-track direction, specifically at track edges of the main pole. Up to now, with regard to the recording characteristics at track edges, attempts have been made to increase the field gradient by reducing the side gap 602 on a side of the main pole 604, an example of which is provided in FIG. 6. However, when the side gap 602 is simply reduced, a problem is encountered in that the intensity of the magnetic field is insufficient because it is absorbed by a side shield, and as a result it is not possible to obtain the desired field gradient.
Accordingly, it would be beneficial to have a recording system where the cross-track gradient and the down-track gradient at track edges of a main pole are increased while limiting, the corresponding decline in field intensity at the track edges to a minimum